Many 5-digit ZIP code numbers are represented by multiple polygons in the TeleAtlas StreetMap Premium sdc file named zip5.sdc. The same-numbered ZIP polygons always seem to be adjacent to each other. What's going on? I wonder if these polygons are actually ZIP+4 polygons that were not dissolved to form the true, larger 5-digit ZIP areas.
BTW, the zip5.sdc file I am using is dated July 20, 2009.
